Characteristics and Application Structure of Special Synthetic Rubber
Special synthetic rubber: styrene-butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber, etc. Characteristics and application structure.
1, styrene butadiene rubber
Structure of Styrene Butadiene Rubber
Styrene-butadiene rubber is a polymer elastomer obtained by copolymerization of butadiene and styrene as monomers in emulsion or solution catalyzed by a catalyst.
Properties of Styrene Butadiene Rubber
L styrene-butadiene rubber is unsaturated rubber, the content of double bonds in its molecular structure is lower than that of natural rubber, and the existence of benzene ring reduces the activity of double bonds, so compared with natural rubber, styrene-butadiene rubber has slower vulcanization speed, less scorching or over-sulfur of rubber compound, and better heat resistance, oxygen resistance, ozone resistance and sunlight aging resistance.
L styrene-butadiene rubber is non-crystalline rubber and needs to be reinforced with carbon black.
L styrene-butadiene rubber has a huge benzene ring in the side group of the molecular chain, the flexibility of the molecular chain is poor, and the internal friction is large. Therefore, its elasticity, strength, flex crack resistance, tear resistance and cold resistance are not as good as those of natural rubber. In particular, heat generation is greater during multiple deformations, and adhesion is poor and adhesion type is more difficult. However, compared with natural rubber, it has better durability and air permeability.
The nonpolar rubber of l styrene-butadiene rubber can be dissolved in hydrocarbon solvent and is not resistant to oil, but its oil resistance is slightly better than that of natural rubber.
L styrene butadiene rubber has low cost.
Use of Styrene Butadiene Rubber
Styrene-butadiene rubber is used in pneumatic tires, rubber shoes, rubber tubes, adhesive tapes, rubber rollers, adhesive tapes and model products through formula adjustment or in combination with natural rubber and butadiene rubber.
2. cis-polybutadiene rubber
Properties of cis-polybutadiene rubber
The molecular structure of L cis-polybutadiene rubber is mainly cis-1,4-structure, with regular molecular arrangement, so its elasticity is better than that of natural rubber. At the same time, its low glass transition temperature (Tg =-105℃), also makes it have very good cold resistance. In addition, cis-polybutadiene rubber has the characteristics of excellent wear resistance, low heat generation, good flex resistance and the like.
L cis-polybutadiene rubber is unsaturated rubber and can be vulcanized with sulfur and the like. Butadiene has no electron-donating methyl group beside its double bond, which also determines the activity of its double bond. It is not as large as natural rubber, so its vulcanization speed is slow, but its aging resistance and heat resistance are good.
L cis-polybutadiene rubber is also crystalline rubber, but its crystallization temperature is low, so its pure rubber strength is small and it needs to be reinforced with carbon black.
L cis-polybutadiene rubber is also non-polar rubber, which can be dissolved in hydrocarbon solvent and is not oil resistant.
L cis-polybutadiene rubber is poor in self-adhesion and processability, easy to roll off during high-temperature mixing, and high in fluidity during storage.
Use of cis-polybutadiene rubber
Butadiene rubber is generally applied to tires, and can also be used for wear-resistant products (such as rubber shoes and rubber rollers), cold-resistant products and shockproof products.
Properties of neoprene
L storage stability
Sulfur-regulated chloroprene rubber contains S-S bonds in the polymerization process, and is easy to generate polymers with 1,2- structure and 3,4- structure. Because the bond energy of S-S bonds is much lower than C-C bonds and C-C bonds, it is easy to break under the influence of various factors, generating new active groups, resulting in molecular bond crosslinking. However, chlorine atoms in the molecular chains of the 1,2- structure and 3,4- structure are easy to fall off, generating active groups that lead to crosslinking or branching of the molecular chains. Therefore, sulfur-regulated chloroprene rubber has poor stability. According to the standards of the Ministry of Chemical Industry, the storage period shall not exceed six months at 30℃ and one year at 20℃. However, the non-sulfur-regulated chloroprene rubber has no S-S bond during polymerization, and is mainly 1,4- structure, with less 1,2- structure and 3,4- structure, and accordingly has good stability.
L chloroprene rubber has a regular molecular structure, is similar to natural rubber, and is easy to crystallize when stretched, so the pure rubber has higher strength.
L has good aging resistance and heat resistance. Due to the electron-withdrawing and shielding effects of chlorine atoms, general rubber is second only to ethylene propylene rubber and butyl rubber, and its heat resistance is equivalent to nitrile rubber.
L has good flame retardancy. A large amount of hydrogen chloride gas is released during combustion, and the self-extinguishing property is good.
L has good oil resistance and chemical corrosion resistance. It is stable in other solvents except aromatic hydrocarbons and chlorinated hydrocarbon oils.
L has good adhesion and can be made into adhesive.
L has good air permeability resistance, second only to butyl rubber and nitrile rubber.
L can be vulcanized with metal oxides (magnesium oxide, zinc oxide).
L has poor low temperature resistance. It is easy to crystallize and harden at low temperature.
L is sensitive to temperature during processing. the roller temperature is above 70℃, which is easy to stick to the roller and burn.
Use of neoprene
It is mainly used for manufacturing industrial products such as heat-resistant transportation belts, rubber pipes resistant to oil and chemical corrosion, container liners, rubber rollers and rubber plates, as well as wires and cables.
4. Butyl rubber Butyl rubber is a linear copolymer produced by ionic polymerization of isobutylene and a small amount of isoprene.
IIR has the lowest permeability among hydrocarbon rubbers.
Because IIR has low chemical unsaturation and polyisobutylene chain is inactive, IIR has better heat resistance and oxidation resistance than other common rubbers. Using heat-resistant compound formula, its maximum use (intermittent use) temperature can reach 180℃.
IIR has excellent weatherability, and its performance changes little when exposed to sunlight and air for a long time. Especially the ozone resistance is 10 times higher than NR.
IIR has strong acid and alkali resistance, and it swells very little in polar solvents such as alcohols, ketones and esters, but it is not resistant to hydrocarbon solvents, and it expands rapidly in aliphatic hydrocarbon solvents.
IIR has good electrical insulation and corona resistance.
IIR has low water permeability, excellent water resistance at normal temperature and much lower water absorption rate than other rubbers at normal temperature.
IER is not easy to crystallize at low temperature and has good cold resistance. The glass transition temperature Ts and brittleness temperature Tb are only the second order BR, IR and NR.
① Large internal friction, large hysteresis loss and large heat generation in high-speed periodic strain. (2) rebound value is much lower than other rubber. (3) The vulcanization speed is slow, requiring high temperature or long time vulcanization. ④ Self-adhesion and mutual adhesion are poor. (5) poor compatibility, poor compatibility with NR and other general rubber, not suitable for use. ⑥ The interaction with filler is poor and good reinforcement effect cannot be obtained. Therefore, the reinforcing effect of carbon black on IIR is small. The masterbatch filled with carbon black needs heat treatment, so as to improve the tensile property, elasticity, abrasion resistance and dielectric property of vulcanizates.
IIR is widely used in tire inner tubes, water tires, vulcanizing capsules, wires and cables, waterproof coiled materials and other aspects due to its low air permeability, low water permeability, excellent heat resistance, weather resistance, ozone resistance, electrical insulation and other properties.